Stair and stairwell constructions of the type mentioned above are especially used in jumbo type aircraft in which at least two decks are interconnected by stairs. The construction of such stairs and their position relative to emergency exits are subject to official regulations which aim at making sure that in an emergency the distances to be traversed between such a stair and the next available emergency exit are as small as possible so that passengers and crew may reach these emergency exits as quickly as possible. Conventional constructions of this type have rigid stairwell enclosure housings which are not suitable for installation near emergency exits. There is also room for improvement with regard to the space requirements for such structures, especially floor space near an emergency exit.